How do you measure a flashlight?
Perhaps the best known measurement is luminous flux, which is measured in lumens. This value shows the total power emitted by a light source weighted by the Λ curve. The Λ curve gives the sensitivity of the eye as a function of wavelength, as the human eye is not equally sensitive to all wavelengths. This may sound complicated at first, but it is easy to understand with a concrete example: for two identical 1 W light sources, if one is green and the other red, then even though they have the same wattage, the green one will have a higher lumen output because the human eye perceives green "better".
The luminous flux of a lamp is measured in a sphere filled with sensors, so that the directional characteristics can be measured at the same time.
Another important and much used measurement is luminous intensity, measured in candela. It is the ratio of the luminous flux, interpreted in a given direction from a source, radiated into an elementary solid angle containing that direction, divided by the solid angle. In more practical terms, it is the power of light emitted in a given direction along a beam.
There is one other figure that comes up regularly in connection with luminaire matters, illuminance, measured in lux. It is calculated as the ratio of the luminous flux (lumen) incident on a surface element containing a given point to the size of the surface element, in effect the lumen incident on 1 nm.
The lux is therefore never a characteristic of the light source, but rather an indication of how much lux a given light source produces on a given surface (which can be misleading because it depends on many things, e.g. from what distance it is measured, etc.)
Colour of the light from the flashlight
The colour temperature of a light source, in this case a lamp, is determined by the colour sensation it produces and the colour sensation created by a hypothetical blackbody radiator. The number characterising the wavelength distribution of the energy emitted in the visible range is the colour temperature. It is measured in kelvin, the sign is K.
The K-value of a light source is not a qualitative question, it only determines the colour of its light. Just as an example, normal summer midday sunlight is about 6000 K, but when it gets cloudy, the colour temperature of the light "goes up" to 10,000 K. Lamps tend to show values between 3000-7000 K, the former a more yellowish light, the latter a little bluer. For comparison, the LED light in cars is 3500 K. The yellowish light is more pleasant to the eye, but the cooler, bluish shade makes things much sharper.
The other important measurement is the colour rendering index, or 'CRI' or 'Ra', which measures the ability of a light source to render the colour of different objects when illuminated. The best available rendering value is defined as 100, while the lowest is 0. Lights usually give a value of 70-80, if better than this, it is emphasised, a value of 95 is considered very good.
Lamp wattage
In the days of traditional bulbs, everyone knew what to expect when they bought a 60 Watt bulb. Now, we are slowly replacing our home light bulbs with LED bulbs, and the change is much more drastic for sports lights, where it is practically impossible to find a conventional bulb or a solution other than LED technology on the market. The energy consumption of LED bulbs is much lower than that of conventional bulbs. This is also true for the bulbs used in sports lights, a small torch can provide a considerable amount of light with a power of only 5 W. Of course, there are also more powerful hand-held spotlights that can draw up to 50 W, but these require a serious power source.
Protection against liquids and solids
Depending on the intended use and the nature of the application, the enclosures of electrical appliances are protected against the ingress of solid bodies and water. They are marked with the symbols of the different IP protection modes and the two numbers indicating the degree of IP protection. Thus, the first digit after IP indicates the protection provided for solids and the second for liquids, and the different meanings of the digits are shown in the table below. If the number is replaced by an X, it indicates a lack of protection.
